Dislocation Networks Strain Fields Induced By Si Wafer Bonding
- PDF / 370,938 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 51 Downloads / 211 Views
Dislocation Networks Strain Fields Induced By Si Wafer Bonding. J. Eymery, F. Fournel*, K. Rousseau, D. Buttard, F. Leroy, F. Rieutord, J.L. Rouvière. CEA/Grenoble, Département de Recherche Fondamentale and *LETI/Département des Technologies Silicium, 17 rue des martyrs, 38054 Grenoble Cedex 9, France. ABSTRACT Buried dislocation superlattices are obtained by bonding ultra-thin single crystal Si (001) films on Si (001) wafers. The twist of two Si wafers induces a regular square grid of dissociated screw dislocations and the tilt a 1-D array of mixed dislocation. The Burgers vector is a/2 for both types of dislocation. The atomic displacements and deformations of pure screw and edge dislocations are calculated with an isotropic elasticity approximation taking into account the free surface and the thickness of the upper crystal. It is shown by these calculations that the elastic strain field propagates up to the surface, and quantitative arguments are given to choose the network period / film thickness ratio. INTRODUCTION The self-assembly of semiconductor quantum dots has attracted a lot of interest in recent years because of their potential applications in novel electronic and optoelectronic devices. Several experiments have been performed to increase the lateral ordering to control the individual properties of the dots. One of them consists to achieve a regular nanometric patterning of the substrate by using a periodic strain field induced by a misfit dislocation network. The control of the island nucleation by buried dislocations has been demonstrated [1], but the network regularity was not enough to induce a lateral ordering. An assembling technique using 4-inch (001) direct wafer bonding and Silicon on Insulator (SOI) wafer [2] has been used recently to obtain high quality ultra-thin Si crystalline layers on Si substrates. This method is compatible with microelectronics technology, and allows an accurate control of the network period. Moreover, the dislocation cores are buried at the interface so that they don’t interact directly with the islands. It has been shown from continuum elasticity calculations [3,4] that the periodic dislocation strain field close to the surface may be used to obtain a controlled surface patterning and to grow selforganized quantum dots with a narrow size distribution. The propagation of the strain field to the surface has been confirmed experimentally by scanning tunneling microscopy. We have observed on bonded substrate [5] a very regular nanoscale surface patterning and the achievement of the long range ordering of Si quantum dots on very thin oxide layers. For a (001) bonded interface, the twist ψ of two Si wafers with flat and parallel (001) surfaces (i.e. no miscut) induces a regular square grid of pure or dissociated screw dislocations, called hereafter twist interfacial dislocations (TWIDs). Whereas a tilt angle θ (miscut angle of the bonded samples) induces 60° or mixed dislocations [2] called tilt interfacial dislocations (TIDs). The Burgers vector is a/2 for both types of di
Data Loading...
